Switch control mechanism



Feb. 17, 1953 W. E. ENGELHARD SWITCH CONTROL MECHANISM Filed Feb. 9, 1951 V I N V EN TOR. WE Engeffi ard B Y 'I ATTORNEY Patented Feb. 17, 1953 UNITED STATES PATENT OFFICE SWITCH CONTROL MECHANISM William E. Engelhard, North Arlington, N. J.

Application February 9, 1951, Serial No. 210,267

2 Claims. 1

This invention relates to a mechanism for the control of a switch or other electrical apparatus. It is particularly directed to such apparatus wherein a part, such as the switch designated in the accompanying drawing by reference character II, is actuated on and off responsive to temperature or other predetermined condition reflected by a member such as is designated in the drawing by reference characters 29 and I5. This reference to the drawings is for the purpose only of facilitating an understanding of the invention, which is not limited to the specific examples shown in the drawings, as will become apparent from the description below.

One of the objectionable features of apparatus heretofore constructed was that the on-off actuation (as of the part II) was not sufficiently responsive to minor changes of condition. The abrupt on-off effect, responsive to degree or other major condition change, resulted in appreciable time lags. This was objectionable as not permitting of control within fractional or very narrow ranges. The invention below described and illustrated in the accompanying drawings provides a smoothing out effect by automatically anticipating the on-off moments and accelerating them automatically, making the action smooth and continuous rather than abrupt and appreciably intermittent.

In the drawings:

Fig. 1 is a schematic view of a mechanism embodying the invention, and

Fig. 2 is a fragmentary perspective view of a mechanism adapted to be used in connection therewith.

As shown in the drawings, the apparatus to be controlled is generally designated by refer ence character It! and may, for example, be the power circuit of an electric furnace or the like. The switch or other part to be controlled is designated by reference character II and responds to movement of the pointer or blocking member 15 which, in turn, reflects the condition at 20 in the apparatus, for example. Part II is actuated to one position on the normal flow of current through the switch circuit I2 to open or close power circuit I0.

The control mechanism of the present invention comprises a resistance unit I3 cut into switch circuit I2, and of such resistance value that it will decrease the passage of current through the switch circuit sufficient to preclude actuation of the switch to the position shown in Fig. 1. The resistance unit I3 may be electrically sensitized, however, by the sensitizing unit I4, to

2 lower its resistance value and thus permit flow of current through circuit I2 sufficient to actuate switch I I. sensitizing unit I4 is connected to a suitable power source I! and is so juxtaposed relative to resistance unit I3 as to sensitize the latter while the space or path I5 between the units is clear.

The apparatus includes a blocking member I6, which maybe a pointer registering on scale 22, for example, said pointer being pivoted as at I8 and being moved by a member I9 (which may be an electro-magnet or other mechanism) responsive to the condition, such as heat, at a point in the apparatus, marked 20, this condition being reflected to actuate member I9 through a responsive device such as indicated by the thermocouple 2|. The pointer I6 will move on its pivot I8 and when it reaches the predetermined point at which it is desired to discontinue the flow of current through the apparatus circuit I0, it will be disposed in space I5 between units I3, I4, interrupting the action of sensitizing unit I4 on resistance unit I3. The units I3 and I 4 might be movable or preset to such position along the scale 22, for example, as will indicate a maximum or other desired range, the attainment of which would be marked by the pointer or blocking member I6 moving into space I5 between the units I3, I4. Disposition of member It in space I5 will permit resistance unit I3 to exert its resistance value which will, in turn, decrease the passage of current to the switch II, opening the switch and thus also the circuit Ill. The effect of the opening of circuit It will be to permit the apparatus being controlled, such as an electric furnace, for example, to return to the desired condition. For example, it will permit a drop in temperature resulting from discontinuance of the flow of current through the apparatus power circuit II! and this, in turn, will, through the reflecting unit 29 and member I9, move pointer I6 out of space I5 between units I3, I 4. Thereupon, the unit M will sensitize the resistance unit I3, permitting the flow of current to be resumed through circuit I2 and through switch I I to close the switch and thus also the power circuit III for the apparatus.

It will be obvious that the cycle described will be automatically repeated again and again. The mechanism of the instant invention accelerates the on-off time by anticipating movement of the blocking member I6 into and out of space I5 between units I3, I4.

This anticipating efiect is obtained by amechanism which subtracts from the current value of circuit I! for sensitizing unit I l when pointer I6 is out of the space I5 and adds to the current value of circuit I! when member I6 is in space I5. Thus, the moment of restoration of flow of suflicient current through unit It on retraction of blocking member I6 from path Iii will be expedited, as will also the moment of drop of current on return of blocking member It to path I5. The effect attained by the present invention, therefore, is to accelerate the on-and-oii' moments of current through apparatus if! to be controlled. The practical effect is to make it possible to control such apparatus within a fraction of a degree of temperature variationwhere that is the condition to be controlled. The mechanism comprises a pair of thermal resistance elements 26, 21, the former having a positive temperature coefficient, the latter a negative cosmcient, said elements being arranged in series in power circuit 11 of sensitizing unit M and being selectively actuated by means, including a switch 25, responsive to the condition of circuit l2 for switch II, which, in turn, reflects the position of blocking member 16 relative to units it, it.

The elements 26, 21 have positive and negative temperature coefficients only when thermally actuated. Elements 26, 21 being opposed, neutralize the effect of room temperature and room temperature changes. Elements 27 are actuated, as shown in the drawings, by heating elements 28, 29, which are selectively controlled by switch 25. The resistance value of each element 26, 21 is such fractional part of the resistance value of circuit H for unit I4 that the latter will receive adequate current through circuit ll to actuate the same for its intended. purpose, notwithstanding the effect of the positive coefficient resistance element. Its effect is to accelerate the moment the intensity of current through circuit I! will become insuflicient for the purpose mentioned.

Pointer I6 approaches the space 55 while the flow of current through circuit l2 closes circuit I0 and energizes relay 25 to connect heating element 28 to power source 36 and thermally energize the positive coeflicient resistance element-as 26, for example. When pointer it" cuts into space I5 between units I3, I4, it will open circuit I0 at an earlier moment than it would have done if element 26 was not then operative to reduce the intensity of current flowing through unit I4. Likewise, the other (negative coefficient) resistance element, as 21, is energized while there blockage of space I5 sufiicient to affect circuit H (which condition of circuit 52 affects relay 25 connected thereto by leads '35) moving the relay 25 to its other position to actuate element 23, heating and thus activating element 2a. The effect of thermally activated element 2? (negative coefficient element) is to add to the intensity of current flowing through sensitizing unit I4 while the pointer is in the path iii, brightening bulb l4. Unit I4 will thus attain intensity of current required to exert a sensltizing effect on unit 13 at a sooner moment of withdrawal of pointer I6 from path iii.

The heating elements 26, 23 are connected to a suitable power source 30, as, for example, a transformer or the like; the transformer, in turn, may be connected to a power source and to elements 28, 29 selectively through switch 25 above described.

As will be appreciated, therefore, the action of the mechanism of the present invention is one of anticipating the condition at 23 so that a smoother control of the electrical part In to be controlled is attained, the on-off connection of parts I9, I2 being effected within a much lesser range of fluctuation of condition than would otherwise be possible.

Fig. 2 is a perspective view illustrating a mechanism which may be used to preclude excessive movement of pointer I6, comprising a guide 36 having upstanding walls 31, 38, to limit the extremes of movement of the pointer or blocking member l6 into and out of the path or space [5 between units I3, I4. The member 36 is preferably made of flexible metallic or similar material, bent to the shape shown in Fig. 2. It has been found that with the use of a guide 36, electrostatic charges cause adherence of pointer I6 to wall or The pointer It is finely balanced so as to move responsive to very slight exertion of power. It will tend to remain stuck to wall 3'! or 38 by virtue of the electrostatic charges. Another feature of the present invention is to provide means for vibrating the guide 36 to preclude sticking or" pointer I6 to a wall of guide 36. This end is attained by mounting the guide 36 rigidly as at 40 on a support GI in a fashion which will permit a slight amount of independent movement of guide 36 relative to said support 4| and mounting an electromagnet 33 on the support 4| to vibrate guide 36 in the fashion of an armature. Mechanism 39 has a core or pin 42 passing through support 4! and spaced as at 30 from the guide 36 so that on flow of alternating current through mechanism 39 a magnetic field will be set up which will vibrate guide 36. The memher 39 may be a resistance coil or other unit connected to an alternating current power source; for example, it may be cut into circuit 11 to lower the value thereof. This has been found of practical value in prolonging the useful life of a bulb I4; it may be connected to another power source. Guide 36 is preferably made of magnetic material, such as pure nickel, the intensity of its vibration depending on the intensity of magnetic field set up at 30, in turn depending on the spacing of the end of core pin 42 from member 36 at 30. Adjustment of that spacing is attained by rotating the pin as at the end 42' thereof so as to prevent such harsh vibration as would whip the pointer I6 from one Wall of guide 36 to another.

In the specific form shown in the drawings, resistance unit I3 is a photoelectric cell and sensitizing unit It is an incandescent bulb having a lens which will focus its light in the form of a beam I5 onto unit l3. It will be apparent that resistance unit I3 may be any other type of resistance unit affected by a sensitizing unit juxtaposed to mark a space line I5 between units I3, I4, sensitizing action of unit it on unit I3 being effective only while said space I5 is uninterrupted. The specific circuit wiring arrangements may be varied as required by the job at hand. It will also be apparent that in place of relays i! and 25, other switch mechanisms suit able to the same end and well known in this art may be substituted. Likewise, the action of the relays may be the reverse of that above described, to suit specific applications, as, for example, to normally open the circuit of apparatus I0 and to close the same only upon the occurrence of a condition at 26.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent is:

1. A control system for making and breaking the electrical circuit to a device experiencing fluctuations in energy level, which comprises a main switch, an electromagnet for controlling said switch adapted to be affected by a predetermined intensity of current supplied thereto, a feed circuit connected to said electromagnet and including a light-responsive resistance unit, a light source in alignment with said unit, means for converting predetermined differences in energy level of said device to mechanical translating movements and a movable blocking member between said unit and light source operated by said converting means, an auxiliary circuit for energizing said light source and including resistors of positive and negative temperature coeificients, selectively operable heating means for said resistors alternately operable by a switch ing device controlled by the intensity of current in said feed circuit to decrease the current in said auxiliary circuit when said feed circuit has closed said main switch and to increase the current in said auxiliary circuit when said feed circuit has opened said main switch, whereby said light source and light responsive resistance unit accelin its REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,685,995 Gano Oct. 2, 1928 1,930,496 Wilson Oct. 17, 1933 2,148,491 Moore Feb. 28, 1939 2,187,613 Nichols Jan. 16, 1940 2,205,777 Fairchild June 25, 1940 2,302,320 Hintze Nov. 17, 1942 2,471,457 Shepard May 31, 1949 FOREIGN PATENTS Number Country Date 640,150 Germany Dec. 23, 1936 

